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Search Results: 1 - 10 of 466669 matches for " Gregory A. Neumann "
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Laser Ranging for Gravitational, Lunar, and Planetary Science
Stephen M. Merkowitz,Philip W. Dabney,Jeffrey C. Livas,Jan F. McGarry,Gregory A. Neumann,Thomas W. Zagwodzki
Physics , 2007, DOI: 10.1142/S0218271807011565
Abstract: More precise lunar and Martian ranging will enable unprecedented tests of Einstein's theory of General Relativity and well as lunar and planetary science. NASA is currently planning several missions to return to the Moon, and it is natural to consider if precision laser ranging instruments should be included. New advanced retroreflector arrays at carefully chosen landing sites would have an immediate positive impact on lunar and gravitational studies. Laser transponders are currently being developed that may offer an advantage over passive ranging, and could be adapted for use on Mars and other distant objects. Precision ranging capability can also be combined with optical communications for an extremely versatile instrument. In this paper we discuss the science that can be gained by improved lunar and Martian ranging along with several technologies that can be used for this purpose.
Extreme Telomere Length Dimorphism in the Tasmanian Devil and Related Marsupials Suggests Parental Control of Telomere Length
Hannah S. Bender, Elizabeth P. Murchison, Hilda A. Pickett, Janine E. Deakin, Margaret A. Strong, Carly Conlan, Daniel A. McMillan, Axel A. Neumann, Carol W. Greider, Gregory J. Hannon, Roger R. Reddel, Jennifer A. Marshall. Graves
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0046195
Abstract: Telomeres, specialised structures that protect chromosome ends, play a critical role in preserving chromosome integrity. Telomere dynamics in the Tasmanian devil (Sarcophilus harrisii) are of particular interest in light of the emergence of devil facial tumour disease (DFTD), a transmissible malignancy that causes rapid mortality and threatens the species with extinction. We used fluorescent in situ hybridisation to investigate telomere length in DFTD cells, in healthy Tasmanian devils and in four closely related marsupial species. Here we report that animals in the Order Dasyuromorphia have chromosomes characterised by striking telomere length dimorphism between homologues. Findings in sex chromosomes suggest that telomere length dimorphism may be regulated by events in the parental germlines. Long telomeres on the Y chromosome imply that telomere lengthening occurs during spermatogenesis, whereas telomere diminution occurs during oogenesis. Although found in several somatic cell tissue types, telomere length dimorphism was not found in DFTD cancer cells, which are characterised by uniformly short telomeres. This is, to our knowledge, the first report of naturally occurring telomere length dimorphism in any species and suggests a novel strategy of telomere length control. Comparative studies in five distantly related marsupials and a monotreme indicate that telomere dimorphism evolved at least 50 million years ago.
The Paradigm of Surgical Ellipse Dimensions: Are the Length-to-Width Ratio of 3 to 4 and a Vertex Angle of 30º Correct?  [PDF]
Tamara R. Tilleman, M. M. Tilleman, M. H. A. Neumann
Surgical Science (SS) , 2013, DOI: 10.4236/ss.2013.44045

Background: It has been postulated that elliptical cutaneous excisions must possess a length-to-width ratio of 3 to 4 and a vertex angle of 30o or less in order to be closed primarily without creating a “dog ear”. These dimensions became axiomatic in cutaneous surgery and have been taught in the apprenticeship model for years. The present article examines the validity of that paradigm. Methods: We collected data from two sources: ellipses described in the literature (57 cases); and elliptical excisions performed at the authors’ outpatient clinic (83 cases). The surgical ellipse lengths, widths, and vertex angles were analyzed, and the data were compared to a mathematical formula used to generate a fusiform ellipse. Results: The length-to-width ratio of 3 - 4 was found to be inconsistent with the recommended vertex angle of 30o. In fact, a length-to-width ratio of 3 - 4 determines a vertex angle of 48o - 63o. A 30o vertex angle is only feasible with long length-to-width ration of about 7.5. Conclusions: The paradigm that surgical ellipses should have a vertex angle of 30o with length-to-width ratio of 3 - 4 is incorrect. Evidence from actual surgical practice and from mathematical formulation shows that either the length-to-width ratio must be larger than 3 - 4 or the vertex angle must be larger than 30 degrees.

Inferring the Ancient History of the Translation Machinery and Genetic Code via Recapitulation of Ribosomal Subunit Assembly Orders
Gregory P. Fournier,Justin E. Neumann,J. Peter Gogarten
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0009437
Abstract: Universally conserved positions in ribosomal proteins have significant biases in amino acid usage, likely indicating the expansion of the genetic code at the time leading up to the most recent common ancestor(s) (MRCA). Here, we apply this principle to the evolutionary history of the ribosome before the MRCA. It has been proposed that the experimentally determined order of assembly for ribosomal subunits recapitulates their evolutionary chronology. Given this model, we produce a probabilistic evolutionary ordering of the universally conserved small subunit (SSU) and large subunit (LSU) ribosomal proteins. Optimizing the relative ordering of SSU and LSU evolutionary chronologies with respect to minimizing differences in amino acid usage bias, we find strong compositional evidence for a more ancient origin for early LSU proteins. Furthermore, we find that this ordering produces several trends in specific amino acid usages compatible with models of genetic code evolution.
Lithography and Fabrication of Frictional Tiers on Poly(Dimethylsiloxane) Using Atomic Force Microscopy  [PDF]
Gregory S. Watson, Jolanta A. Watson
Journal of Surface Engineered Materials and Advanced Technology (JSEMAT) , 2012, DOI: 10.4236/jsemat.2012.223036
Abstract: This study investigates controlled micro/nano manipulation of polydimethylsiloxane (PDMS) using Atomic Force Microscopy (AFM). Lithographic results revealed stick-slip phenomena along the slow scan direction. Varying the normal loading force, scan size, scan number and contact conditions allowed the control of certain lithographic outcomes e.g., channel spacing. The PDMS surface experienced significant in-plane deformation in response to the tip-induced lateral force. This displacement increased with increasing loading force, creating greater spacing between channels in the slow scan direction. Simultaneous generation of a lateral displacement in the fast scan direction caused a decrease in channel length with increasing loading force due to an increase in static friction with normal force, resulting in a greater surface relaxation, and shorter track length of dynamic friction. By controlling both the loading force and the number of scans over an area, frictional tiers were produced.
Long Term Survival in a Patient with Anaplastic Thyroid Carcinoma Treated with Cricotracheal Resection  [PDF]
Gregory Sayer, Douglas Sidell, Joel A. Sercarz
International Journal of Otolaryngology and Head & Neck Surgery (IJOHNS) , 2012, DOI: 10.4236/ijohns.2012.12008
Abstract: Anaplastic thyroid cancer is an uncommon malignancy with a poor prognosis. Elderly patients are most commonly afflicted and survival past 3 years occurs in less than 5% of patients. Management of these patients is challenging, and the importance of palliation, airway protection, and aggressive resection is debated. In this report, we describe a patient with anaplastic thyroid carcinoma who presented with respiratory distress due to invasion of the tracheal cartilage. The patient was managed with cricotracheal resection, total thyroidectomy and thyrotracheal anastomosis. The patient is currently disease free 3.5 years after resection and postoperative radiation therapy with interval neck dissection.
Were There Commercial Communications between Prehistoric Harappans and African Populations?  [PDF]
Kenneth A. R. Kennedy, Gregory L. Possehl
Advances in Anthropology (AA) , 2012, DOI: 10.4236/aa.2012.24020
Abstract: This paper is an historical and scientific evaluation of Western archaeologists’ theories concerning ancient population movements and commercial contacts between the prehistoric Harappans and African populations during the Indus Age (2500-1900 BC). In this context the human skeletal remains and artifacts from Harappa and Mohenjodaro are relevant. An urnburial from the Indus river site of Chanhudaro has an important bearing upon this subject. The scientific aspect of this study is the provision of hitherto unascertained data to palaeoanthropologists anaylsing the skeletal and dental biology of prehistoric populations of South Asia.
A Review of Artificial Immune System Based Security Frameworks for MANET  [PDF]
Lincy Elizebeth Jim, Mark A. Gregory
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2016, DOI: 10.4236/ijcns.2016.91001
Abstract: Mobile ad hoc networks (MANETs) are collections of wireless mobile devices that form a communication network with restricted broadcast range, limited resources and without fixed infrastructure. Routing is a critical function in multi-hop MANETs. At the same time, security in MANETs—especially routing security—presents a number of new and interesting challenges. Communication is achieved by relaying data along routes that are dynamically discovered and maintained through collaboration between the nodes. Advances in the field of artificial immune systems provide an opportunity to improve MANET security and performance. Artificial immune systems mimic the functionality of the human immune system wherein there is clear distinction between self and non self and this delineation is important in a MANET where there is no centralized management. The high level of protection provided to the human body by an evolved immune system can be applied as a security feature in MANET. The current security techniques proposed for MANET have varying degrees of success due to the dynamic nature of a MANET. This paper will review different strategies for the application of artificial immune systems to MANETs.
Process-Based Friction Factor for Pipe Flow  [PDF]
James M. Gregory, John A. McEnery
Open Journal of Fluid Dynamics (OJFD) , 2017, DOI: 10.4236/ojfd.2017.72015
Abstract: The Moody Diagram is widely used to determine the friction factor for fluid flow in pipes. The diagram combines the effects of Reynolds number and relative roughness to determine the friction factor. The relationship is highly non-linear and appears to have a complex interaction between viscous and boundary roughness effects. The Moody Diagram is based on predictions from an equation developed by Colebrook in 1939. The relationship requires an iteration process to make predictions. While empirical relationships have been developed that provide good predictions without an iteration process, no one has fully explained the cause for the observed results. The objective of this paper is to present a logical development for prediction of the friction factor. An equation has been developed that models the summed effect of both the laminar sublayer and the boundary roughness on the fluid profile and the resulting friction factor for pipes. The new equation does not require an iteration procedure to obtain values for the friction factor. Predicted results match well with values generated from Colebrook’s work that is expressed in the Moody Diagram. Predictions are within one percent of Colebrook values and generally less than 0.3 percent error from his values. The development provides insight to how processes operating at the boundary cause the friction factor to change.
Probing of a parametrically pumped magnon gas with a non-resonant packet of traveling spin waves
T. Neumann,A. A. Serga,B. Hillebrands
Physics , 2008, DOI: 10.1063/1.3050530
Abstract: The magnon gas created by spatially localized longitudinal parametric pumping in an yttrium-iron-garnet film is probed by a traveling packet of spin waves non-resonant with the pumping field. The analysis of the influence of the magnon gas on the amplitude and phase of the propagating spin waves allows to determine characteristic properties of the parametrically pumped magnon gas. A simple theoretical model is proposed from which the magnon density in the pumping region is calculated.
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